Proppant

Abstract

A proppant comprises a particle and a polycarbodiimide coating disposed on the particle. The polycarbodiimide coating comprises the reaction product of an isocyanate reacted in the presence of a phospholene oxide catalyst. A method of forming the proppant comprises the steps of providing the particle, providing the isocyanate, providing the phospholene oxide catalyst, reacting the isocyanate in the presence of the phospholene oxide catalyst to form the polycarbodiimide coating, and coating the particle with the polycarbodiimide coating.

Description

RELATED APPLICATIONS[0001]This application is a continuation in part application of U.S. patent application Ser. No. 13 / 126,905, which is the national stage of International Patent Application No. PCT / EP2009 / 064244, filed on Oct. 29, 2009, which claims priority to and all the advantages of U.S. Provisional Patent Application Nos. 61 / 109,226 and 61 / 229,093, filed on Oct. 29, 2008 and Jul. 28, 2009, respectively.FIELD OF THE INVENTION[0002]The subject invention generally relates to a proppant and a method of forming the proppant. More specifically, the subject invention relates to a proppant which comprises a particle and a coating disposed on the particle, and which is used during hydraulic fracturing of a subterranean formation.DESCRIPTION OF THE RELATED ART[0003]Domestic energy needs in the United States currently outpace readily accessible energy resources, which has forced an increasing dependence on foreign petroleum fuels, such as oil and gas. At the same time, existing United ...

AI Technical Summary

Benefits of technology

[0012]Advantageously, the proppant of the subject invention improves upon the performance of existing proppants. The performance of the proppant is attributable to the polycarbodiimide coating. In addition, the proppant of the subject invention is formed efficiently, requiring few resources.

Problems solved by technology

Domestic energy needs in the United States currently outpace readily accessible energy resources, which has forced an increasing dependence on foreign petroleum fuels, such as oil and gas.

At the same time, existing United States energy resources are significantly underutilized, in part due to inefficient oil and gas procurement methods and a deterioration in the quality of raw materials such as unrefined petroleum fuels.

However, many existing proppants exhibit inadequate thermal stability for high temperature and pressure applications, e.g. wellbores and subsurface reservoirs having temperatures greater than 70° F. and pressures, i.e., closure stresses, greater than 7,500 psi.

That is, many existing proppants comprise coatings, such as epoxy or phenolic coatings, that break down or shear off the particle in an uncontrolled manner when exposed to such high temperatures and pressures.

Also, many existing proppants do not include active agents, such as microorganisms and catalysts, to improve the quality of the petroleum fuel recovered from the subsurface reservoir.

Further, many existing proppants comprise coatings having inadequate crush resistance.

That is, many existing proppants comprise non-uniform coatings that include defects, such as gaps or indentations, which contribute to premature breakdown and / or failure of the coating.

Since the coating typically provides a cushioning effect for the proppant and evenly distributes high pressures around the proppant, premature breakdown and / or failure of the coating undermines the crush resistance of the proppant.

Crushed proppants cannot effectively prop open fractures and often contribute to impurities in unrefined petroleum fuels in the form of dust particles.

Moreover, many existing proppants also exhibit unpredictable consolidation patterns and suffer from inadequate permeability in wellbores, i.e., the extent to which the proppant allows the flow of petroleum fuels.

That is, many existing proppants have a lower permeability and impede petroleum fuel flow.

Further, many existing proppants consolidate into aggregated, near-solid, non-permeable proppant packs and prevent adequate flow and procurement of petroleum fuels from subsurface reservoirs.

Also, many existing proppants are not compatible with low-viscosity carrier fluids having viscosities of less than about 3,000 cps at 80° C. Low-viscosity carrier fluids are typically pumped into wellbores at higher pressures than high-viscosity carrier fluids to ensure proper fracturing of the subterranean formation.

Consequently, many existing coatings fail mechanically, i.e., shear off the particle, when exposed to high pressures or react chemically with low-viscosity carrier fluids and degrade.

Finally, many existing proppants are coated via noneconomical coating processes and therefore contribute to increased production costs.

That is, many existing proppants require multiple layers of coatings, which results in time-consuming and expensive coating processes.

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